1. Field of the Invention
The present invention relates to an oil-absorbing material for treating oil-contaminated water which is useful for purifying such oil-contaminated waste streams as industrial waste water or municipal sewage and to a process for its preparation.
2. Description of the Prior Art
Methods of treating oil-contaminated waste water such as flotation, filtering, adsorption, and electrolysis have been suggested hitherto but are all very inefficient when the oil in the waste water is stabilized by being emulsified and dispersed.
Activated carbon and fibrous thermoplastic resins are already well known as waste water treating materials and activated carbon is extensively used for decolorizing and deodorizing water. Fibrous thermoplastic resins such as polyolefins are extensively used to treat waste water containing spilled oil or floating oil.
However, some waste water contains not only floating oil and suspended dispersed oil, but also emulsified dispersed oil. For example, when a high performance surface active agent is used to wash ships or machines, substantially all the oil content will become emulsified and dispersed in the waste water. Furthermore, as a result of the wide use of various surface active agents, even household waste water contains emulsified dispersed oil. The above mentioned activated carbon and fibrous thermoplastic resins shown substantially no oil collecting activity on waste water containing such emulsified dispersed oil and they are especially poor when the oil-contaminated waste water contains a nonionic surface active agent which emulsifies and disperses the oil.
Hence, a need has existed for an oil-adsorbing material capable of removing dispersed and emulsified oil contaminants from water.